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38 GOLF COURSE MANAGEMENT 08.14
Winning the
mosquito war
with Bt
Twilight. The best time of day to play golf.
The air is cool, the wind is calm and the sun
is mellow. Friends leave work and meet for a
leisurely nine. Tag-along kids like to work the
ball washer and rake out bunker footprints.
The sun sets a little lower and then a tiny sound
like razors across an overtuned violin threatens
to cut the evening short. One swat, then a slap
and splat, and eventually the evening belongs
to the mosquito.
Mosquitoes can become a threat to rev
-
enue as well as to the health of humans, do-
mestic animals and wildlife. So why is it so
hard to control a wisp of an insect no bigger
than a dandelion seed? Sheer numbers are on
their side. However, it also may be due to the
fact that this pest goes unnoticed until the
adult stage. Synthetic pesticides used to control
adult and larva are generally nonselective and,
as such, can negatively impact benefcial in
-
sects. Effective biological control can be a less
lethal alternative to achieve control early in
the mosquito's lifespan.
Bacillus t ingienisis (Bt) is a biological
control that acts upon the mosquito larva be
-
fore becoming an adult. The mosquito un-
dergoes complete metamorphosis: egg, pupa,
larva and adult. During the larva stage, the
mosquito feeds and lives in water. It is only
during this larva stage that the mosquito is
susceptible to Bt control. The Bt bacteria para
-
lyze the digestive system of the larva and effec-
tively starve it to death (Cranshaw, W.S. 2008.
Colorado State University Extension, Bacillus
t ingienisis Fact Sheet No. 5.556, www.ext.
colostate.edu/pubs/insect/0556.pdf ).
Bt is not a silver bullet. The same principles
of turf pest management must be applied to
achieve mosquito control. Understanding the
biology and habitat of the mosquito is essential
to developing a multi-pronged control strategy.
The superintendent must monitor pest levels
and properly time Bt applications. Developing
an integrated pest management approach en
-
ables the manager to achieve success with bio-
logical controls.
Eliminate mosquit abitat. The most basic
management strategy is to identify and elimi
-
nate stagnant water and overgrown vegetation.
Mosquitoes lay eggs in stagnant and slow-mov
-
ing water. They thrive in areas where exces-
sive vegetation provides moisture and cover
from predators. Mosquito larvae live in aban
-
doned tires, poorly drained ditches, potholes,
plugged drains, water-holding bunkers, etc. Be
certain that no areas are regulated as wetlands.
Do not drain wetlands.
Mosquito biology. Mosquito life cycles can
vary due to climate and species. Check with
a local Extension offce to gain a clearer un
-
derstanding of species life span in your area.
Generally, adults can live up to 14 days. The
larva stage spans about seven to 14 days. Some
mosquito species are daytime biters and some
bite only at night. Daytime biters can come
from several miles while nighttime biters
are from shorter distances (Biological Notes
on Mosquitoes, www.mosquitoes.org/Life
-
Cycle.html ). Check with an entomologist for
identifcation if adults are present while your
monitoring of nearby water bodies indicates
no larvae activity.
Pamela C. Smith, CGCS
Greenskeeper99@yahoo.com
Monitoring and timing. Bt applications need
to be done during the larva stage. If stagnant
waters cannot be drained, weekly monitor
-
ing should begin in spring. A white dipper is
used to remove about a cup of water. Inspect
the water for the dark-colored wiggler larvae.
If no larvae are present, check the label to see if
preventive applications are allowed. When lar
-
vae are present, treat according to label recom-
mendations. Check for larvae after rain events
in addition to weekly monitoring. Rain events
can move Bt-treated waters, leaving an area
ripe for new larvae.
To test Bt effcacy, place a few grains of
product in a container with stagnant water and
several larvae. Larvae should expire within one
to three days of being exposed to Bt.
Read t e label, record and report. There are
several commercially available Bt pesticides.
Bt products can be granular or in the form of
dunks (little pucks). Bt products are labeled as
pesticides and should be treated as such. Read
the label and apply only according to label di
-
rections. Check the local, state and federal ap-
plication and reporting requirements prior to
using any pesticide on or near a body of water.
Some application sites may require a permit to
apply to waters regulated by private and gov
-
ernmental agencies.
Bt biological control can be an effective
control of mosquito pests. However, Bt use re
-
quires diligent monitoring and understanding
of mosquito biology and habitat. Proper use of
Bt can eliminate the reliance on nonselective
synthetic pesticides and, in turn, protect bene
-
fcial organisms essential to a balanced ecology.
Pamela C. Smith, CGCS, is the director of agronomy for a
large city and a 23-year member of GCSAA.
Bacillus thuringienisis (Bt) products for controlling mosquitoes come in several forms, including little
pucks. Photo by Pamela Smith
Presented in Partnership
with Aquatrols
(environment)